The study, by Alexis Conason, PsyD, of the New York Obesity Research Center, and colleagues also found a link between a specific operation, laparoscopic Roux-en-Y gastric bypass surgery, and an increase in alcohol use after the procedure. The findings appear in the Oct. 15 online issue of Archives of Surgery.

"We're only talking about a minority of patients here," Conason says. "But what we're seeing is some patients who seek out bariatric surgery have a history of using food to deal with emotions."

When such patients no longer can overeat as a way to cope with their feelings, they may turn to "other external coping mechanisms like drugs or alcohol," Conason says.

The study looked at 132 women and 23 men who underwent either Roux-en-Y -- one of the most common weight loss surgeries -- or laparoscopic adjustable gastric band surgery to treat their obesity. Participants answered questionnaires about their behaviors and history of drinking or drugs before their surgery and then again one, three, six, 12, and 24 months after their operations.

"When we looked at each substance (drugs, alcohol, and cigarette smoking) individually, we didn't see a huge difference, but when you looked at the whole group, we saw a significant increased risk for drug and alcohol use at the two-year point after the surgery," says Conason. "Our findings are important because it raises some concerns about who is at risk."

Struggling With a New Body

Nearly 36% of the adult U.S. population is obese. Some 200,000 adults have bariatric surgery each year, according to the American Society for Metabolic and Bariatric Surgery.

Psychological profiles vary among severely obese patients seeking bariatric surgery. Conason says patients' issues range from depression and anxiety to loneliness, difficulty dealing with relationships, and dealing with the social stresses of being obese.

Many bariatric surgery patients may lose 60% of their excess body weight within a year. The change can be emotionally shocking for some patients.

"Many of these people have struggled with obesity their entire lives, and in a very short period of time, they literally develop these new bodies," Conason says. "Patients will walk by a mirror and say they don't recognize themselves. Their weight loss changes how family and friends relate to them. They're getting different kinds of attention, and it's a lot to adjust to. For many patients, bariatric surgery often lifts their depression, but other patients may struggle with their new bodies."

Erik Dutson, MD, is the director of bariatric surgery and executive medical director of the Center for Advanced Surgical and Interventional Technology at the UCLA Health System in Los Angeles. He says that surgeons are aware of some bariatric surgery patients being at risk for substance abuse.

"It's referred to in our circles as addiction replacement, which isn't unique to bariatric surgery," Dutson says. "If they're using food in this way and they undergo bariatric surgery, they can't go back to eating the way they did, and the brain's reward system becomes starved."

Mental Health Care Critical After Weight Loss Surgery

Bariatric surgery patients are screened by mental health professionals before they undergo the procedure. During this evaluation, they are advised to avoid alcohol, because it can damage the gastrointestinal tract lining. Patients must be tobacco-free for three consecutive months prior to undergoing the operation. If someone is identified as having an eating disorder such as bulimia, says Dutson, the patient is referred for longer-term therapy.

"It's possible patients aren't always forthcoming during the pre-surgery evaluation," he says. "But in my experience, by the time patients want bariatric surgery, they're in the mentality mode of, 'I need to get this taken care of.' Those circumstances push people toward honesty."

The positive body changes that follow weight loss surgery offer a psychological boost. But adjusting to the post-surgery world has its ups and downs, says Kelli Friedman, PhD, director of psychology at the Duke Center for Metabolic and Weight Loss Surgery in Durham, N.C.

"There's not a lot of scientific study on this topic, but like this study, we also think that two years after the surgery appears to be a particularly vulnerable time for patients," she says. "Many surgery centers have the presurgical psychological evaluation and offer follow-up care, but we need to do a better job at long-term follow-up care, not just a few months after surgery."

Friedman points out that a patient's alcohol metabolism changes after bariatric surgery.

"A patient who has lost a significant amount of weight after bariatric surgery may feel the effects of alcohol much quicker than they were used to," she explains. "Mental health providers need to continue working closely with these patients so we can identify who is at risk and check in on them periodically."